1. Field of the Invention
The present invention relates to certain polymeric materials having substantially modified surfaces which are inherently antimicrobial. The invention also relates to selective irradiation and chemical reducing processes for preparing the antimicrobial materials of the invention, methods of using such antimicrobial materials to control microorganisms, and products and devices comprising such antimicrobial materials.
2. Description of the Prior Art
Although there is no disclosure of imparting antimicrobial properties, laser irradiation of fibers, yarns, and nonwoven materials is known. PCT. Application WO 87/03021, published May 5, 1987, discloses the irradiation of such materials to form depressions and elevations on the surface which improves the material's adhesiveness, frictional resistance and absorptive capacity.
Polyamide materials can also be irradiated with electron energy or treated chemically for grafting purposes, or for improving certain mechanical properties. United Kingdom Patent, 1,078,457, discloses treating polyamide materials with stabilizers such as sodium and potassium borohydride for protecting the materials from discoloration and loss of mechanical strength when exposed to heat or light. Nablo, U.S. Pat. No. 3,774,706, discloses a process of using substantially monochromatic, short-period, high intensity electron beams at a dosage rate considerably in excess of 10.sup.7 rads/second to bulk-sterilize a wide range of substances. Nablo, U.S. Pat. No. 4,211,622, discloses using electron energy to graft phosphorous or halogen-rich double bonded molecules into materials such as nylon in order to impart flame retardant properties. Tamura et al., U.S. Pat. No. 4,291,142, discloses crosslinked aromatic polyamide films which may be crosslinked by means of heat, ultraviolet (UV) rays, or electron beams. The crosslinked film shows an increased resistance to thermal decomposition. Calcaterra et al., U.S. Pat. No. 4,810,567, discloses a class of antimicrobial fabrics having one or more antimicrobial agents covalently bonded to a graft copolymer of the fabric. The graft copolymer may be formed by electron beam irradiation of a fabric impregnated with a vinyl monomer.
It is also known that antimicrobial properties can be imparted to certain types of acrylic polymers, fibers and fabrics. Pardini, U.S. Pat. No. 4,708,870, discloses an antimicrobial composition of a) at least 85% by weight acrylonitrile, b) up to about 13% by weight of a neutral ethylenically unsaturated monomer, and c) from-about 0.1 to 10% by weight of a protonated amine containing compound. The composition is formed by copolymerization of the acrylic protonated amine comonomer and/or by use of protonated amine end groups.
In accordance with the present invention, it has now been discovered that certain polymeric materials having substantially modified surfaces are antimicrobial. It has also been discovered that selective ultraviolet (UV) photon irradiation, electron irradiation, or chemical reducing agents can impart this property to the polymeric material.